Intraoperative probes become increasingly important in the surgical management of cancer. Attempts with gamma probe guided surgery to improve the completeness of surgical excision of radioiodine avid tissues in thyroid cancer have been performed through several decades. The first Polish results by Pomorski et al. have shown that gamma probe guided surgery after preoperative dose of 131I have allowed locating and increasing the completeness of thyroid excision. These results have been substantiated by other authors. However, in the evaluation of intraoperative gamma probe localization of 131I avid tissues one should remember of the limitations of the method. The article begins with a discussion of the statistical limitations of the radiation detection and of the key performance parameters that characterize detectors. Later on we continue with the description of specific aspects concerning gamma probe guided surgery in thyroid cancer.